Chitosan–silica composite aerogels: preparation, characterization and Congo red adsorption

A series of aerogels composed of chitosan and/or silica were fabricated by tuning their feeding ratios. They were characterized by FTIR, thermogravimetric analysis, and X-ray diffraction; pore structures were analyzed by Brunauer–Emmett–Teller (BET) nitrogen sorption and scanning electron microscopy (SEM); adsorption capacities to Congo red were explored as well. The incorporation of silica enhances the thermostabilization of chitosan in gels. And as silica content increases, bulk densities of aerogels decrease gradually, while porosities, pore volumes, and surface areas obtained via BET method increase consequently; as well, porous structure becomes more regular and pore size tends to be smaller that was observed by SEM. The adsorption capacities of chitosan-containing aerogels to Congo red reach as high as about 150 mg/g, much higher than that of pure silica (17 mg/g), demonstrating their potential as a class of novel adsorbent materials. Graphical Abstract: [Figure not available: see fulltext.]A series of chitosan- and/or silica-based aerogels were fabricated, which were named as C5S0, C4S1, C1S1, C1S4, and C0S5, with different designed CS/SiO₂ mass ratios of 100/0, 80/20, 50/50, 20/80, and 0/100, respectively. Their compositions and structures as well as adsorption properties to Congo red were analyzed and compared in detail.